Can you explain the motions of the medial and lateral meniscus and their relation to the screw home mechanism?

The “screw-home” mechanism is considered to be a key element of knee stability and is required for standing upright. It is a rotation movement that occurs between the tibia and femur. It occurs at the end of knee extension, between 15 and 20 degrees of knee flexion and full knee extension. The tibia rotates internally during the swing phase and externally during the stance phase. External rotation occurs during the terminal degrees of knee extension and results in tightening of both cruciate ligaments, which locks the knee. The tibia is then in the position of maximal stability with respect to the femur.

Between full flexion and extension, the mean meniscal excursion is 5.1 for the menial meniscus and 11.2 for the lateral meniscus. The P/A ratio (the ratio of posterior to anterior meniscal translation during flexion) is 1:2.4 for the medial meniscus and 1:1.3 for the lateral meniscus. (pg 15 in the link).

Reference 1, Reference 2: Thompson W O. Am J Sports Med, 1991, 19: 200 – 216.